Field of the Disclosure
The present disclosure relates to wireless communication systems, and more particularly to techniques for supporting telematics-enhanced emergency calls from mobile phones.
Description of Related Art
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, space and power). Examples of such multiple-access systems include code-division multiple access (CDMA) systems, time-division multiple access (TDMA) systems, frequency-division multiple access (FDMA) systems, and orthogonal frequency-division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple wireless devices. Base stations may communicate with wireless devices on downstream and upstream links. Each base station has a coverage range, which may be referred to as the coverage area of the cell.
One application in which wireless communications systems are increasingly being used is establishing emergency calls. Wireless communications systems can provide not only a communication channel for transmitting and receiving voice content, but can also provide additional information, such as the location of the caller, to a public safety answering point (PSAP) that responds to the emergency call. In some instances, the wireless communications system itself may determine the location of the caller and provide the location to the PSAP, but in other instances, the wireless communications system may not be able or willing to provide this information to the PSAP. In those instances where the wireless communications system does not (or cannot) provide the additional information to the PSAP, the device placing the emergency call may provide the additional information, such as the location of the caller, to the PSAP via a communication session signaling protocol. The PSAP may, for example, request a set of data from the device, and the device may respond by sending the requested set of data to the PSAP. Not all devices, however, may be compatible with the communication signaling protocol and thus certain devices may not be able to provide the requested set of data to the PSAP.
One example of a wireless communication system used to support emergency calling is eCall, a European system that integrates wireless connectivity into vehicles to enable the vehicle to establish emergency calls in case of a crash or other event. Vehicles that are eCall capable can send the current location of the vehicle to the responding PSAP in a set of data, commonly known as a minimum set of data (MSD), but may need to do so in-band with the voice connection between the vehicle and the PSAP if, for example, the network coupling the vehicle with the PSAP is a circuit-switched network.
Adapting the eCall in-band signaling protocol to a personal emergency call initiated from a mobile phone may enable transfer of a caller location from the mobile phone to the PSAP, but may also have a side effect of muting of the voice channel for several seconds while the location information is requested by the PSAP and transmitted by the mobile phone. While this muting side effect may be tolerable if it is known to a certain level of confidence that the mobile phone can in fact provide the requested information, the muting may be undesirable in cases where the mobile phone cannot provide the requested information.